The cost of treating people infected with the Human Immunodeficiency Virus (HIV) and people with AIDS (PWAs) places a heavy burden on our health care system. The need to identify and appropriately allocate the resources required for the treatment of these patients is a vital national concern. This research study is designed to measure the actual hospital inpatient resources required, as identified by the specific type and number of services, for the care of HIV-infected persons and PWAs. The specific aims of the project are: 1) to develop a profile of the inpatient hospital services provided to HIV-infected patients assigned to DRGs 488, 489, and 490, 2) to develop a profile of the inpatient hospital services provided to PWAs assigned to each of the major severity stages of the Severity Classification System for AIDS hospitalizations, 3) to determine the variations in the use of hospital inpatient resources for HIV-infected persons and PWAs according to their payor source. This study utilizes the International Classification of Clinical Services coding system to determine and measure the laboratory, imaging and pharmaceutical services provided to HIV-infected persons and PWAs. We believe this coding system is an efficient mechanism for measuring clinical resource use. The profiles developed with this system can serve to measure current treatment patterns, determine differences in treatment patterns over time and across institutions, detect differences in treatment patterns by patient and provide a basis for the development of national health care policy.